Recently, various organizations including the government, companies, and universities deal with a large amount of various data, so that the data are managed by using a comparatively large-scale storage apparatus(es). Such a large-scale storage apparatus is constructed by arranging a plurality of storage devices (for example, hard disk drives) in an array. For example, one or more hard disk drives constitute one RAID (Redundant Arrays of Independent Disks) group and one or more logical groups are defined in physical storage areas provided by one RAID group. Then, these logical volumes are provided to a host system. The host system can write or read data by sending a specified command to the logical volume(s).
Since the above-described storage apparatus processes a large amount of various data, it is required to have high performance. So, in order to achieve high performance of the storage apparatus, a microprocessor package (hereinafter referred to as the MPPK) which takes charge of data processing such as data writing to and reading from the logical volumes is decided in advance and control information required for data processing is stored in a local memory in the MPPK. Under this circumstance, an MPPK which takes charge of processing of a certain logical volume is called an owner MPPK and this MPPK will be hereinafter referred to and explained as having ownership of the relevant logical volume.
Furthermore, Patent Literature 1 discloses a technique to relocate the ownership of a certain logical volume to another MPPK according to a resource status and response performance of the storage apparatus and distribute processing load on MPPK's.